Combine parallel processing with swim lanes?

Question

I want to build something like this using PlantUML:

But I'm only able to build this:

This is my code:

@startuml
start
:Init;
fork
:Treatment 1;
fork again
:Treatment 2;
end fork
@enduml

Answer 1

As far as I understand Activity Diagrams

• you can parallelize things into swimlanes, but there's only one start
• everything has to be in a swimlane (so I proposed "Control" as the start of your diagram)
• PlantUML (and maybe UML in general) expects you to have a join after a fork (which again, I did in the "Control" lane):

@startuml
|Control|
:Init;
fork
|#AntiqueWhite|Swimlane1|
'start
:foo1;
'stop
fork again
|Swimlane2|
'start
:foo2;
:foo3;
'stop
|Control|
end fork
stop
@enduml

The PlantUML layout also isn't ideal, since the fork line stays only in the swimlane of the Control process.

Answer 2

This is possible by combining an extra column for forking and hiding the start arrows:

@startuml
| | 
|a| Swim1
|b| Swim2
|c| Swim3
| |
fork
|a|
-[hidden]->
start
    if (A?) then (no)
        stop
    else (yes)
        if (B?) then (no)
            stop
        else (yes)
            :C;
        endif
    endif
stop
fork again
|b|
-[hidden]->
start
    :Process 2;
stop
fork again
|c|
-[hidden]->
start
    :Process 3;
stop
| |
end fork
@enduml

Answer 3

Would like to add

skinparam activityBarColor white
skinparam swimlaneBorderColor white

to Mazzy's answer, if you don't mind missing borders of the lanes and don't need additional forks in your diagram.

or invert the lane background color

Answer 4

Not a complete solution but:

@startuml
start
:Init;
fork
start
:Treatment 1;
end
fork again
start
:Treatment 2;
end
end fork
@enduml

see also:

• the code through the plantuml web server: http://www.plantuml.com/plantuml/uml/SoWkIImgAStDuG8pkAmyyp9BhBdIyekoOI8XHQc99RcfUIKAXjPSgNafO4c5nFJ4p3nC9KPW9I2i03R30SW2cWu0
• the corresponding png: